For certain kinds of wood, dust which is generated during the operation of a tool (e.g. a sanding tool) may be fine and lightweight, and therefore potentially detrimental to health. For this reason, the tool is often combined with a device for preventing the release of dust into the surroundings so that the operator is not exposed to excessive amounts of dust while he or she is working.
In order to prevent or lower the emission of dust, mechanical filters such as a screen, mesh, sieve, paper bag or cloth have been combined with the tool which generates the dust. However, fine dust is difficult to filter out effectively. Such mechanical filters may become clogged or completely closed within a relatively short time. If this happens, the efficiency of the filter is reduced and dust is no longer prevented from reaching the local environment. Moreover, the tool may come to a standstill due to electric overload.
For dust generated by wood and other materials such as concrete, standards have been developed indicating for how long a worker may stay in air which contains a certain percentage of dust. In order to meet these standards, the aforementioned filters have to be cleaned from time to time or replaced. This may be costly in terms of time and money.
For preventing the release of very fine dust, fine dust filters are available. However, these filters are very expensive. Electrostatic filters are similarly expensive. In some cases, water has been used as a filtering means. However, such filtering means require permanent supervision and eventual replacement. Moreover it may be difficult to apply such filtering means with an everyday tool or a tool which is used by non-specialists (e.g. do-it-yourself enthusiasts) or which is used in different working positions.
Cyclones are known to be effective filters for separating dust from a gas. Such cyclones have relatively large dimensions and are widely used in chemical plants. U.S. Pat. Nos. 4,373,228 and 4,593,429 describe the application of a cyclone for separating dust front air in a vacuum cleaner.